1. Field of the Invention
The present invention relates to ultrahigh pressure fluid containment systems, and in particular, to components, systems and methods for sealing ultrahigh pressure fluids between components.
2. Description of the Related Art
Systems for containing fluids at ultrahigh pressures, such as those in excess of 15,000 psi, can be extremely complicated and subject to failure after an unacceptably short life span. One example of an ultrahigh pressure system is illustrated in FIG. 1, wherein a cylinder 10 is compressed by tie-rods 12 between a check valve 14 and a plug 16. A fluid at an ultrahigh pressure is contained within a cavity 18 (FIG. 1a) that is sealed between the cylinder 10, the check valve 14 and the plug 16. Although various methods have been used to provide a seal for such a configuration, as discussed below, the methods have shown to be insufficient.
As best illustrated in FIG. 1a, an annular seal 20 fabricated from a sacrificial material of lower strength than the cylinder 10 and the check valve 14 is positioned between the two bodies to provide a seal. It has been found, however, that the lower strength seal 20 requires frequent replacement, and that the stresses exerted by the seal result in early failure of the primary complements of the system. Such failures include cracks 22 formed in the bodies adjacent the annular seal 20.
In addition, because materials subjected to extremely high pressures expand, relative motion between the parts results in failure through spalling, galling, or fretting. As best illustrated in FIG. 1b, as the pressure within the cylinder 10 cycles between atmospheric pressure and ultrahigh pressures, the cylinder and the plug 16 expand and contract. It has been discovered that, in the configuration illustrated in FIG. 1b, the cylinder 10 moves at a different rate as compared to plug 16. As a result, during each cycle there is relative movement between the parts. Relative movement between parts of like materials in compression results in spalling, galling and fretting, each of which can damage one or both of the abutting components and shorten the life of the system.
Although this example is illustrated with a drawing of a plug, a cylinder and a check valve, it has been experienced in the industry that similar failures occur at other locations throughout an ultrahigh pressure fluid containment system. Accordingly, the invention discussed below is intended to solve such problems throughout the system.
The present invention is directed toward components, systems and methods for sealing between components in ultrahigh pressure fluid containment systems. Embodiments of the invention allow a complete seal to be formed without a gasket between components of a like material. In addition, embodiments of the invention allow adjacent components to expand and contract without significant relative motion between the components, reducing damage and extending the useful life of the components.
One embodiment of the invention incorporates a pair of adjacent components, one having a tapered female mouth integrally formed thereon for engagement with a complementary tapered male mouth integrally formed on the adjacent component. Each of the mouths has a mating portion. One of the mating portions has a substantially linear cross-sectional profile that is angled between 40 and 68 degrees from a longitudinal axis of the coupling. The other of the mating portions has a convex, curved cross-sectional profile that engages the linear profile of the other component at a substantially circular seal. The system allows components of like materials to be sealingly engaged with each other without the need of a gasket between the components.
Another embodiment of the present invention is directed toward a body having a tapered mouth configured to mate with a complementary mouth on a pressure vessel to form a circular seal therebetween. A contact angle between the adjoining components is tangential to at least one of the components, the tangent measuring between 40 and 60 degrees from a longitudinal axis of the component.
The present invention is also directed toward methods of manufacturing such components.